1. Field of the Invention
Generally, the present invention relates to improving the reliability of motors used in electrical equipment in automobiles, i.e. a starter motor, a wiper motor, a power window motor, a power seat motor, a sunroof motor and the like. Specifically, the present invention relates to a composition that is impregnated on the armature coil of an electrical motor to improve the motor's reliability by withstanding the onset of cracks due to great differentials in temperature.
2. Description of the Related Art
In electrical motors, a copper armature coil is wound around a slot formed in an iron armature core. The copper armature coil is fixed to the iron armature core by a resin composition (fillers) impregnated in between the armature coils within the slot. The composition protects the armature coil, or projection thereof, from abrasions when the armature is rotating at high speeds. Without the resin composition, the armature coil or projection thereof may break, or an insulating film, which is commonly used, may peel off. Thus the composition is important in maintaining the reliability and life of an electrical motor.
When an electrical motor, such as a starter motor, is located near an automobile engine, it can be subjected to internal temperature differentials ranging from as high as 150.degree. C. to as low as -40.degree. C. or below. Such temperature differentials are common during cold weather conditions when an automobile engine has been running for a period time, and then turned off. Electrical motors that are continually subjected to great differentials in temperatures are unreliable and have short operating lives because the composition cracks. Until now, the need for an electrical motor that can withstand great temperature differentials has existed.